In the rivers: Multiple adaptive radiations of cyprinid fishes (Labeobarbus) in Ethiopian Highlands

Boris A. Levin,Yury Y. Dgebuadze,Alexander S. Golubtsov,Evgeniy Simonov,Marina Levina

doi:10.1038/s41598-020-64350-4

Abstract

Multiple repeated patterns of adaptive radiation were revealed in cyprinid fish inhabiting the compact geographic region of the Ethiopian Highlands. We found four independently evolved radiations in the evolutionary hexaploid (2n = 150) Labeobarbus lineage based on matrilineal relationships of >800 individuals. Each radiation displayed similar patterns of mouth phenotype diversification, and included ecomorphs/species of the generalized, lipped, scraping (one or two), and large-mouthed (one to three) types. All radiations were detected in geographically isolated rivers, and originated from different ancestral populations. This is the first documented case in which numerous parallel radiations of fishes occurred–via different ways–in a riverine environment. Some radiations are very recent and monophyletic, while others are older and include ecomorphs that originated in separate mini flocks and later combined into one. The diversification bursts among Ethiopian Labeobarbus were detected in the mid-upper reaches of rivers (1050-1550 m above sea level), which likely offer ecological opportunities that include diverse habitats yet poor fauna (i.e. lower competition and relaxed selection). This promising example of parallel evolution of adaptive radiation warrants further investigation.

Highlights

The origin of biodiversity is one of the most intriguing questions in evolutionary biology and ecology
Phylogeny of Labeobarbus in the Ethiopian Highlands. Both Bayesian inference (BI) and maximum likelihood (ML) analyses supported the division of Ethiopian Labeobarbus into two clades representing the eastern (L. gananensis/L. jubae complex) and western (L. intermedius supercomplex) parts of the Ethiopian Highlands, with L. ethiopicus (Zolezzi 1939) as an outgroup (Fig. 3)
The most important result of our study is the evidence for repeatedly evolved similar patterns of ecological diversification in a compact geographic region

Summary

Introduction

The origin of biodiversity is one of the most intriguing questions in evolutionary biology and ecology. The main prerequisites for adaptive radiation are: (1) environmental stability for evolutionarily significant periods (starting from thousands of years ago); and (2) physical isolation from the river drainages harboring diverse fish faunas[15,20,31]. The latter serves a dual purpose: first, it provides the ecological opportunities for niche divergence at the initial stages of radiation, and later it prevents the extinction of diverged forms caused by competition with highly specialized species from other systematic groups. The segment of the Genale River that harbours the radiating assemblage of distinct forms of the Labeobarbus is situated in the apparently old canyon, isolated by the Baratieri Falls from the lower reaches of the river system and characterized by the depauperate fish fauna[20]

Objectives

Methods

Results

Conclusion